1. Field of the Invention
This invention relates to a method of and an apparatus for inspecting a bottle or the like using an optical device to determine presence or absence of a defect by electronic processing.
2. Description of the Prior Art
Various methods of optically inspecting a bottle or the like to determine the presence or absence of a defect such as, for example, a split often referred to as a check or a foreign article such as a stone or the like) which may appear at or mixed in a bottom or body portion of the bottle are conventionally known. An exemplary one of such methods is disclosed, for example, in Japanese Patent Publication Application No. 58-58020. According to the method, light is irradiated in an inverted conical ring shape by a light projecting section upon circumferential side wall of a bottle for inspection from above such that it may be introduced toward a bottom face of the bottle so as to reach a corner material portion of the bottom through the material of the side wall of the bottle. The light which is reflected from a split in the corner material portion is introduced into a single photoelectric transducer element to detect such a split.
The method, however requires an optical system which is complicated in construction. In addition, since reflected light is detected only by means of the single photoelectric transducer element, if the angle of light reflected from a check is different only a little from a specified angular range, such reflected light will not be introduced into the photoelectric transducer element, and consequently, the presence or absence of a defect cannot be detected accurately. Further, various design patterns are commonly formed on bottom faces of bottles, and the amount of reflected light is varied to a great extent depending upon such design pattern. Accordingly, it is impossible to detect a check of a bottle only from a variation in amount of light when the bottle has a design pattern thereon.
Another exemplary one of such conventional methods as described above is disclosed in Japanese Patent Laid-Open Application No. 61-107144. According to the method, a bottle is carried in to an inspection position in the neighborhood of a one-dimensional image sensor, and while the bottle is being rotated around an axis thereof with the axis thereof held in parallel to a longitudinal direction of the image sensor, it is illuminated such that an image of transmission light through the bottle is formed on the image sensor. The image sensor is scanned so as to obtain a set of signals, and such scanning &s repeated during rotation of the bottle so as to successively obtain a plurality of sets of signals. Two sets of signals obtained at a first rotational position of the bottle and a second rotational position of the bottle after rotation of the bottle from the first rotational position are compared with each other, and presence or absence of a defect is determined in accordance with a result of such comparison.
With the method, the accuracy in detection is somewhat higher than that of the former method described above. However, while employment of a one-dimensional image sensor is more advantageous in regard to resolution than employment of a two-dimensional image sensor, a high degree of accuracy cannot be anticipated for detection of a check of a bottle using a one-dimensional image sensor since the direction of reflected light from a check of a bottle is changed to a great extent by rotation of the bottle and since such checks are various in shape and further since more disturbance light from other than a check is received by the one-dimensional Image sensor due to rotation of the bottle. Accordingly, the latter method cannot cope efficiently with cheeks of bottles having various shapes.